(1. 中南大学 冶金科学与工程学院, 长沙 410083; 2. 广西师范大学 化学化工学院，桂林 541004)
摘 要: 以可溶性锂盐、铁盐及有机碳源为原料，通过真空高温固相合成法，同时得到两种LiFePO4/C纳米复合材料(分别来源于直接固相合成和气相沉积)。采用XRD、SEM、TEM及电化学工作站对复合材料的结构及电化学性能进行分析和研究。结果表明：来源于气相沉积的LiFePO4/C复合材料具有良好的结构和电化学性能，LiFePO4颗粒大小为50~200 nm，碳膜的厚度为5~10 nm；在0.05C倍率下放电比容量为170 mA∙h/g，接近LiFePO4材料的理论比容量；以1C、2C、5C倍率放电，放电容量分别是理论容量的83%、77%、62%；1C倍率下进行充放电循环50次后，容量衰减只有0.27%，表明材料具有良好的倍率放电性能和循环性能。
关键字: 锂离子二次电池；磷酸铁锂；阴极；复合材料；纳米材料
vacuum heat solid-phase method
（1.School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
2. School of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin 541004, China）
Abstract:Two kinds of LiFePO4/C nano-composites from direct solid-phase synthesis and vapor deposition respectively were obtained simultaneity through vacuum heat solid-phase method using soluble lithium salts, ferric salt and organic carbon as raw materials. XRD, SEM, TEM and electrochemical workstation were used to analyze the structures and electrochemical properties of composites. The result shows that the LiFePO4/C composite from vacuum vapor deposition has good structure and excellent electrochemical performance; the size of LiFePO4 particle is 50−200 nm and the carbon membrane thickness is 5−10 nm; the specific capacity is 170 mA∙h/g when discharged at 0.05C, which is close to theoretical capacity of LiFePO4 materials. When discharged at 1C, 2C and 5C, the specific capacities of nano-composite are 83%, 77% and 62% of the theoretical capacity, respectively, indicating that the sample has good discharge capability at large current rate. The LiFePO4/C nano-composite also shows excellent cycling stability with only 0.27% capacity fade after being charged-discharged for 50 cycles at 1C current rate.
Key words: lithium-ion secondary battery; LiFePO4; cathode; composite; nanomaterials
